Wednesday, September 25, 2013

Luna 17, the spacecraft that carried the Lunokhod-1 rover to the surface of the Moon; debarking ramps for the rover tracks around the lander are visible, extending southeast, to the right. LROC Narrow Angle Camera (NAC) frame M175502049RE, LRO orbit 10998, November 9, 2011; angle of incidence 57.78° at 43 cm per pixel resolution from 30.66 km over 38.23°N, 325.01°E. View the original contextual image with an enlarged inset HERE [NASA/GSFC/Arizona State University].

Samuel Lawrence
LROC News System

Repeat imaging of anthropogenic targets on the Moon remains an LROC priority as the LRO Extended Science Mission continues. These continuing observations of historic hardware and impact craters are not just interesting from a historical standpoint - each image adds to our knowledge of lunar science and engineering, particularly cartography, geology, and photometry.

Making sure that the lunar cartographic network is accurate is a critical component for planning future lunar missions for both human and robotic exploration of the Moon. The historic spacecraft serve as benchmarks (especially the laser retroreflectors). When new images arrive and final ephemeris is in hand we can check if the hardware has moved - well, actually we see the level of uncertainty in computing latitude/longitude coordinates (currently about ±15 meters).

View of the Luna 17 lander from the Lunokhod-1rover (the vehicle descended from its position atop the lander from the opposite side). A wide variety of images, including many other firsts from the Soviet Union's lunar exploration program of the Cold War era can be viewed HERE.

Currently the United States has no near-term plans to land humans or robotic spacecraft on the Moon, however China is scheduled to launch the Chang'e 3 mission in December. If we are lucky, the LROC team might have a before picture to compare to any after pictures of the Chang'e 3 landing site (the exact planned landing coordinates have not yet been released). Currently all LROC NAC investigations must rely solely on "after" images of landing sites. Obtaining a before and after set of images of the Chang'e 3 will facilitate a much better understanding of the delicate processes involved in regolith redistribution due to lander rocket plumes.

When a spacecraft lands on the Moon in a powered descent, exhaust gases from the descent engine disrupt the surface resulting in visible changes around the landed vehicle. These changes can be better understood with photometric studies using using LROC NAC images taken with different illumination geometries. Close to (or right under) the lander the soil is most disrupted, leading to reduced reflectance. Interestingly a zone of increased reflectance surrounds the lander. This "blast zone" ranges from a few meters for the Surveyor spacecraft, to a few tens of meters for Luna, and a few hundred meters for Apollo.

The Apollo 15 landing site through shifting shadows of a simulated lunar day, courtesy of the LROC Featured Sites Index. Very little appears to have changed since the departure of Scott and Irwin nearly 600 lunar days ago [NASA/GSFC/Arizona State University].

Photometric modeling indicates possible causes for the increased reflectance zones from smoothing of the surface by the exhaust flow, the destruction of micro-scale regolith structure, and/or the redistribution of fine particles from the area beneath the lander to its surroundings. Modeling the dynamics of rocket exhaust plumes and studying the exhaust plume effects of previous landed spacecraft on the Moon are defining safe operational practices for future landing sites and outposts.

Exceptionally detailed photograph of the Ranger 9 impact on the floor of Alphonsus crater appears to include an inner disk of darker material around 10 meters across, possibly melt created by the release of kinetic energy, LROC NAC M170579736R, LRO orbit 10272, September 13, 2011; angle of incidence 16.1° at 49.6 cm per pixel resolution from 44.64 km [NASA/GSFC/Arizona State University].

Selection of spacecraft impact sites imaged from LRO using the LROC twin Narrow Angle Camera instrument, all at the same scale [NASA/GSFC/Arizona State University].

Careful retracing of the Lunokhod 2 traverse dramatically improved our understanding of the surface activities of that intrepid rover. In addition, by accurately determining the locations of the Luna 23 and Luna 24 landers, the LROC team determined not only how the Luna 23 spacecraft failed, but also that the Luna 24 sample was collected on the rim of a small impact crater, providing an explanation for the discrepancies that existed for the past three decades between samples and remote sensing of the Mare Crisium surface.

Check out a map of robotic spacecraft sites on the lunar surface, HERE.

(a) listing of coordinates (mean Earth/polar axis (ME) system) of ... Soviet and American robotic space hardware and craters produced through spacecraft impact (thus far) identified by the LROC Team can be download as an Adobe PDF file is available HERE.

To generate the list of observed latitudes and longitudes, we compiled a list of line and sample coordinates for the center of each object in each image. Each image was then initialized using the USGS Integrated Software for Imagers and Spectrometers (ISIS) software package, attaching the appropriate spacecraft position and pointing information, along with the GLD100 lunar shape model for elevation. ISIS routines were then used to compute the latitude and longitude of the spacecraft (or impact crater) in that image.

The LRO spacecraft positions on the list were provided by the latest cross-over corrected spacecraft positioning kernels provided by the LRO LOLA Team, with an orbital position uncertainty of 15 meters. Finally, temperature-corrected NAC camera kernels produced by the LROC team contributed to the high precision and accuracy. The coordinates listed in the table are statistical median from all of the images acquired before April 28, 2013 for a particular site.

From the second of two sequential, exceptionally low periapsis orbital passes, allowing the LROC team at Arizona State University to capture breathtaking views of the Apollo 16 landing site in the nearside Southern Highlands, LRO orbit 10950, November 6, 2011; LROC NAC M175179080, field of view 145 meters, released on the 40th anniversary of the lift-off from the Moon of the Young and Duke expedition, April 22, 2012 [NASA/GSFC/Arizona State University]

The largest of three Apollo lunar laser range reflectors (LLRR), deployed at Hadley Rille by Scott and Irwin of Apollo 15 in February 1971. The instrument is still an active, critical component of on-going experimental science, part of the effort to further constrain the measured distance to the Moon (to within 3 mm) in part determine "locality," if any, of the laws cosmological physics. AS15-85-11468 [NASA/JSC].

An interesting report in the Washington Post relates that the current Mars rover Curiosity (MSL) has found no evidence for methane on that planet, a finding that contradicts some earlier reports of the presence of that gas in the martian atmosphere. The report goes on to say that this finding “disappointed” some members of the Curiosity science team. Supposedly after earlier studies detected methane in telescopic spectra, they had “high hopes” for a positive result from the Curiosity rover.

Various reactions to this revelation are interesting, as they suggest something about the current mania for the search for extraterrestrial life, as well as something about the ultimate rationale for our national space program.

Whence comes this obsession and why does it drive our space efforts and dominate space news coverage? Science fiction dreams have long been a part of the space effort, with many working in the field receiving their first exposure to space topics via that medium played out in print, film and video. From bug-eyed Martians invading the Earth to slimy, acid-dripping killers stowed away aboard spacecraft, the obsession with extraterrestrial life took firm hold of the human imagination.

This sense of fascination is so strong that space advocates have tried to harness it as a way to justify (if not coerce) increased amounts of spending on the civil space program. After the end of the Apollo program, with its clearly geopolitical goals accomplished, the space program needed a new long-term rationale, one that would ensure its continuation over many years. Carl Sagan, an astronomer fascinated by the possibility of life on other worlds, emerged as the principal spokesman for the idea that searching for ET was the “true and good” rationale for exploring space. The dominant theme of his television series Cosmos was the vastness of the universe with endless possibilities for finding life “out there.” For a public television program, it was a huge hit (but to keep some perspective, in 1980 when the series first aired, it did not crack even the top thirty, which included such fare as Dallas, The Dukes of Hazard, and The Love Boat).

Seeking to justify federal spending on space, the Quest for Life Elsewhere (QFLE, as I shall call it) was enthusiastically adopted by the scientific community. As a slogan it was catchy, but effectively got nowhere in terms of policy influence until 1996, with the discovery of what was claimed to be bacterial microfossils in ALHA 84001 (a meteorite that on the basis of several lines of evidence, we believe comes from Mars). This rock has tiny features that resemble fossil bacteria as seen in Earth rocks. This discovery was considered sensational at the time and even resulted in a nationally televised Rose Garden statement by the President of the United States. More significantly for policy, the Mars scientific community parleyed that discovery into a program series of robotic missions, each one increasingly more ambitious (read: expensive) to be sent to Mars over the coming decade(s). This mission series was established outside the agency’s traditional lines of mission proposal and accountability systems and became (in effect), an “entitlement” for the Mars science community and JPL, who possesses the agency monopoly on missions to Mars.

A series of increasingly sophisticated spacecraft were then sent to Mars over the next few years, each one finding that the planet at one time had liquid water at or near its surface and that the climate of the planet has changed, perhaps many times, over the course of its history. But no evidence of extant or former life has been found. As portrayed in the article, this latest finding is another dashing of the “hopes” of the Mars scientists. Funny – I always thought that the job of the scientist was to describe the universe as it is and how it works, not to “hope” for a confirmation of one’s preferred hypothesis (gained through the eyes of a machine afforded almost human-like adoration).

Which brings us to my point above about the use of QFLE as a rationale for the American civil space program.

Seasonal, or at least periodic, remote detection of Methane in the tenuous martian atmosphere may be evidence of biotic activity [ESA].

The goal of adopting such a rationale is to ensure an enduring, long-term space exploration program. From a practical perspective, the danger of using QFLE as the primary goal for space is that if you do not find life, you’ve essentially failed and have probably written your programmatic obituary. To date, the Mars science community has pled for a verdict of incomplete – we simply have not yet gone to the correct place with the correct tools and techniques to verify what they “hope” to find. If this rationalization works, Mars exploration becomes an endless program – we can always say this, no matter wherever we go on Mars and whatever we find. In fact, the problem with that rationale is that such pleading may backfire. When most people think of alien life, they have images of ET in mind, not pond scum. If the public understood that’s what we are really looking for, I suspect that a lot of the support for this crusade would quickly dissipate (I believe much of it has already).

My objection to using the QFLE as a rationale for space is on a more philosophical level. Even if you finally do find martian microbes, what have you proven? There are virtually no modern scientists who do not (to some degree) subscribe to the materialist paradigm of life’s origins, in which given the right compositions, energy and environment, life will naturally arise and evolve. This is what scientists believe about the Earth and they most certainly believe it about other planets. So if we finally do find Mars microbes, either ancient or existing, all we would have done is to prove something that most scientists believe now anyway. The stridency of many scientists in their obsession to obtain “proof” of extraterrestrial life seems like other agendas are at work here, which I pass over without comment.

In science, new findings come all the time and it is highly likely that this “negative” result will soon be countered by some new and compelling “evidence” to the contrary. I think that a long-range strategic rationale to explore and use the Solar System requires re-thinking. A space program needs to return societal value for its cost. I believe that there is abundant value in making our near-term goal the creation of a flexible and permanent system that opens up space for many different and varied uses. Making the space program a Quest for Life Elsewhere is a prescription for failure and ultimately, termination..

Lichtenberg crater (19 kilometers in diameter) is located in western Oceanus Procellarum (31.85°N, 292.28°E). Originally thought to be Copernican in age due to its visible ray system,

Lichtenberg is now thought to be Eratosthenian in age. It turns out that Lichtenberg rays are highly reflective due to their composition and not their relative youth (compositional ray vs maturity ray). Today's Featured Image is an oblique view of Lichtenberg crater and the surrounding terrain. Oblique images are similar to what an astronaut in orbit around the Moon would see looking out a window towards the horizon, and these views are different than most of the LROC NAC images that are taken at nadir (looking straight down).

Lichtenberg crater, super-positioned on the vast basalt flooded nearside plains of Oceanus Procellarum that are, in turn, superimposed nearly over a more ancient, larger "ghost crater" to the northeast. Lichtenberg was originally selected as a Constellation Region of Interest (ROI) for, among other reasons, a distinct younger flow of melt superimposed on the crater's southeastern frontier, demonstrating this part of Procellarum was inundated both before and after Lichtenberg's formation. LROC Wide Angle Camera (WAC) monochrome (604 nm) mosaic from observations collected in sequential orbits July 27, 2011, from approximately 43 km overhead. View a wider field of view in the original mosaic HERE [NASA/GSFC/Arizona State University].

Because oblique images are taken by looking at an angle, these images can enhance or reveal features that may not be evident when looking straight down. For example, Lichtenberg's raised rim is prominent in this image, as is the topographic high within the ghost crater beside it. The diameter of the ghost crater (29 kilometers) suggests that it is a complex crater with a central peak that was subsequently buried by mare basalts. Perhaps a now deeply buried central peak is reflected in the surface as a distinct topographic high in the center of the ghost crater? It is the presence of this flooded crater that caused Lichtenberg to form in an asymmetrical fashion. This viewing geometry also enhances Lichtenberg's textured ejecta blanket, revealing a partial embayment of the ejecta on the eastern side. By applying our understanding of the principles of stratigraphy, the history of this area can be unraveled. A complex crater formed on the surface and was buried by mare basalt. Then, Lichtenberg formed on part of the partially buried rim of the ghost crater. Finally, a new flow of mare basalt partially flooded the ejecta of Lichtenberg.

Wednesday, September 11, 2013

A relatively recent impact event distributed bright, reflective ejecta across the lunar surface in southeast Mare Tranquillitatis. Smaller craters punch through the ejecta to reveal darker substrate, a contrast easier to see under a high Sun, and thus a lower illumination angle of incidence. A 500 meter-wide field of view from LROC Narrow Angle Camera (NAC) observation M139782204LE, spacecraft orbit 5733, September 22, 2010; a 10.11° angle of incidence, resolution 49 cm per pixel from 44.54 km over 4.37°N, 19.29°E [NASA/GSFC/Arizona State University].

Drew Enns
LROC New System

Fresh (young) impacts on the Moon often display magnificent ejecta blankets (so called because they "blanket" the surrounding terrain). Ejecta is unevenly distributed, which gives rise to its interfingered appearance.

Since space weathering tends to lower the albedo of material on an airless planet, the relative brightness of this ejecta blanket speaks to the young age of the parent crater.

In this case, the parent crater is just to the south of the opening image, and can be seen in the context image.

The same small, relatively fresh crater at local sunrise, when shadows under a higher illumination angle of incidence exaggerate variations in topography over albedo. Even so, the brighter surface rays are as distinct as striations channeled into the terrain by the blast. An 1875 meter-wide field of view from LROC NAC frame M162181924L, LRO orbit 9035, June 8, 2011; 73.88° angle of incidence, resolution 0.83 meters per pixel from 39.7 km [NASA/GSFC/Arizona State University].

But what is providing the small circular patches of dark material? Were the patches formed as part of the impact that formed the ejecta blanket, or later? Was the material excavated from below the bright ejecta? Most likely secondary craters (late stage ejecta) from the initial impact, hit and dug up dark mare material (original surface) from below the thin ejecta blanket. Can we test this idea? How dark is dark? In a more precise sense - do the albedos of the small low reflectance spots match that of the surrounding mare?

LROC Wide Angle Camera (WAC) context for the LROC Featured Image released September 10, 2013, showing the field of view located at located at 4.408 N, 19.230 E (marked by the cross). Nearby linear depressions (one smaller, closer depression is visible in the preceding image) may have provided the darker substrate discussed [NASA/GSFC/Arizona State University].

Your eye could be fooled by all the changes in reflectance. The small dark patches have a higher albedo than the mare (0.07 vs 0.06), which would be consistent with mare material mixing with the brighter (0.09 to 0.11) ejecta blanket. This observation is consistent with the secondary crater interpretation (the underlying mare is mixed with a small amount of the bright immature ejecta). If the reflectance of the dark patches was lower than that of the mare, then something else would have to be at work.

Can you think of other explanations while browsing the full LROC NAC frame, HERE?

LADEE, launched from the Mid-Atlantic Regional Spaceport on Wallops Island at 0327 UT, September 7, was the first flight for the Minotaur V and NASA's first Moon launch from Wallops Island.

Shortly after LADEE separated from the rocket, NASA realized the spacecraft's reaction wheels, which stabilize its orientation in space, had shut down too soon. Analysis on Saturday revealed pre-programmed safety limits had caused the switch-off, so NASA disabled the limits to allow the wheels to spin.

Generally speaking, I hate “mop up” posts wherein stories, anecdotes, factoids and announcements are lumped together solely for the purpose of clearing the writer’s desk. But that’s what I have here, so let’s get on with it.

Despite being written off by many as a dead letter topic, the Moon (an object of scientific and commercial interest and utility) continues to confound experts and frustrate naysayers.

You may have recently learned about yet another discovery of lunar water. The “new” this time around is that we have apparently succeeded in identifying a form of hydration (i.e., the OH molecule) present in mineral structures in the central peak of the mid-latitude crater Bullialdus (20.7° S, 22.2° W; 60 km diameter). Past identifications of lunar water involve either the polar dark regions or high-latitude, solar wind implanted OH and H2O molecules.

We’ve known about water-bearing minerals in the lunar samples for the past couple of years, but this is the first time we have identified them using remote sensing. This water is present in extremely minute amounts (tens of parts per million); it has nothing to do with the possibility of extracting water for human use, but rather, is a clue to the hydration state of the deep interior, and ultimately, the origin of the Moon.

We are finding that the early Moon had its own indigenous water, not an obvious consequence of the giant impact origin model, and that this water participated in early melting events. Water is an important compound in these processes by lowering the threshold temperatures of various significant reactions and creating an environment in which explosive, volatile-charged volcanic eruptions may occur. Work continues on understanding the meaning and significance of this interior water to the geological processes of the Moon.

The latest edition of the Global Space Exploration Roadmap has been released and to the astonishment of the press and many other observers, human lunar return is still prominently featured (minus NASA) in the strategic pathways considered by the world’s space agencies. This shouldn’t really surprise anyone – the international partners were taken aback (and angered) by the unilateral renunciation of lunar return by the U.S. in 2010. They have remained firm and consistent in their belief and knowledge that the Moon is a critical step toward developing genuine space faring capability, a path which they have no intention of abandoning. In this, our partners show more insight and sophistication than we do. There are simply too many advantages in developing technology and practicing operational skills on the Moon, all applicable to future human missions beyond low Earth orbit. In a sop to the reluctant Americans, human near-Earth asteroid missions are mentioned. But in the minds of the international partners, the benefits of human lunar return will not be subsumed by a domestic political agenda.

I am an occasional member and contributor to the Lunar Exploration and Analysis Group (LEAG), an informal working group of lunar scientists, engineers and developers who have devised a “roadmap” (i.e., a sequenced, strategic plan) for lunar exploration. This roadmap has been completed and we have developed a couple of ancillary products – an executive summary booklet (being readied for distribution), which will describe the major findings of the three-year road mapping exercise. It will be illustrated by wonderful Technicolor artwork of missions and surface activities (the creation of pretty pictures and graphics we have down pat), and a one-page “fact sheet” describing the value and rationale for human lunar return. The compact fact sheet is particularly good. It summarizes the main points about lunar return, its value to the nation and to science and society in general. This roadmap follows a lot of the concepts about which I write. If you visit Develop Cislunar Space Next, you will recognize many of the same themes and ideas. I am very happy with this product; it is concise and well crafted. I thank my LEAG colleagues for their scientific insight and technical acumen.

About 15 years ago, I wrote a reasonably well-received book published by the Smithsonian Institution Press titled The Once and Future Moon. In it I described the then-recent findings from the Clementine and Galileo missions about the Moon’s processes and history, and summarized what we had learned about the Moon from the Apollo missions. I also took the opportunity to make the case for a return to the Moon (some things never change) and how we might use it to create new capabilities in space. That book is now out of print, as well as rendered somewhat antiquated by the explosion this last decade of new information from data returning from lunar robotic missions and subsequent studies. Many have urged me to revise that book and I am considering writing an updated second edition. Unfortunately, the Smithsonian Press terminated their “Library of the Solar System” series and is not interested in publishing a new edition (but will give me copyright to the material). I am investigating the interest of other publishers and will keep you posted on what develops.

Next – an announcement. For some time I have watched the progress of many of the Google Lunar XPRIZE competitors. It’s a mixed bag, with some teams pretty much out of the running and some who have a decent chance to actually fly a mission. I have been very impressed with the team and the approach of one company, Moon Express (MoonEx), located at NASA Ames Research Center in California. Moon Express has plans for small and medium class lunar landers, using a soon-to-be-unveiled design that seems both robust and affordable. I have agreed to be associated with them on a part-time basis as their Chief Scientist. As such, I will evaluate possible mission scenarios and profiles, devise sample payloads, identify possible instruments and their investigators and vendors, and help define measurement requirements and operational scenarios.

I like working with small missions (my first mission experience was with Clementine (1994) a small DOD-NASA mission, and I was the Principal Investigator for the Mini-SAR radar experiment on India’s Chandrayaan-1 mission) and believe that these small missions deliver a lot of scientific and exploratory bang for a reasonably small amount of bucks. I have worked previously on projects with some of the Moon Express personnel, including Principal Systems Engineer Steve Bailey on the world’s first private lunar lander project (Blastoff.com in the late 1990s) and with CEO Bob Richards, when we were both affiliated with Odyssey Moon a few years ago. I am also happy that my longtime colleague and NASA Advisory Council member Jack Burns has joined the company on a similar part time basis as Chair of the Moon Express Science Advisory Board. I look forward to helping Moon Express achieve their goal of winning the Google Lunar XPRIZE and developing a truly commercial system to deliver payloads to the Moon.

Look for an article on the origin of the Moon written by yours truly, coming soon to a special web-based edition of Astronomy magazine. I’ll post the information when it appears. My recent post here at Air & Space describes the call for small lunar lander missions. The last of the (currently planned) NASA missions to the Moon (was launched Friday, September 6, 2013. Here’s wishing LADEE a safe, successful and productive journey.

So I’m happy to report that there are signs of “life” about our future on the lunar frontier.

Saturday, September 7, 2013

In planning since 2008, LADEE's reason-for-being emerged from mapping science goals believed essential before any permanent manned presence on the Moon's surface could begin. Fortunately, like LRO, LCROSS and GRAIL, planning and development were well underway and within budget when Congress eventually scrubbed the Constellation brand and manned Altair lander [NASA].

What might seem a low-priority mission, accompanied by an appropriate degree of "hype," and has modest fundamental goals under the banner of experimental modular designs and revolutionary high speed communications, - only a 100 day science mission, LADEE has been in development for more than five years. The advanced vehicle also carries with it hopes of some that go back nine times that period, covering a lot of political ground and many changes, even over the relatively short time since its framing and approval.

Gene Cernan (by Harrison Schmitt) at the close-out of the third and final EVA of Apollo 17, and the last manned visit to the Moon in December 1972. The commander's spacesuit is blackened by exceeding fine lunar dust, more than just a problem of appearances, a real hazard that might have caused hatch and spacesuit seals to fail on a longer surface mission. Constellation planners understood they needed to get a handle on mitigating the hazard posed by omnipresent dust while also gaining an better understanding of the dynamics of a primal airless Moon and its surface before humans return to stay [NASA/JSC].

Few watching the LADEE/Minotaur V launch, critical for Orbital Sciences Corporation, from Wallops Island, are likely to be reminded that the mission owes its existence to the catastrophic loss of Space Shuttle Challenger ten years ago. But it is possible to appreciate the things NASA logically wants emphasized without forgetting LADEE is the beginning of the end of the defunct Constellation program that so many wanted dead and buried in 2009.

LADEE is the last of the unmanned precursor missions once believed essential before "extended human activity" on the Moon could begin. The absolutely remarkable Lunar Reconnaissance Orbiter (LRO) will likely still be orbiting the Moon for a few years after LADEE's mission-terminating guided impact a few months from now, but none of these 21st century American unmanned lunar missions are likely to have have occurred before today without the initial political will put in motion after the report of the Challenger Accident Investigation Board (CAIB).

LRO, LCROSS, GRAIL and now LADEE each owe their reason for being to the loss of a second Space Shuttle and crew in 2003.

Very simple schematic of the lunar exosphere. The Moon's surface turned out to be a very dynamic place, after all, with water and exotic metals and volatiles trapped in permanent shadow and also hiding in plain sight [Halekas/LEAG/NASA].

If you've seen the movie footage of Neil Armstrong immediately after setting that first boot on the Moon, backing away from the ladder tethered to the spacecraft then you may have guessed there once was real fear that he might just suddenly disappear in a bog of dust.

Such concern had mostly been dispelled by July 1969, though, after none of the successful unmanned Surveyor landers had encountered anything other than a hard-packed lunar surface. And yet the Moon was correctly presumed to be a very dusty place, constantly "gardened" by micrometeorites (and some not so micro) together with energetic cosmic and solar radiation. Without direct samples, however, no one correctly guessed just how "fine" the dusty powder on the lunar surface could be.

By the time Gene Cernan climbed back into the Apollo 17 lunar module in late 1972 at the end of the program another hazard from this dust had become apparent instead. Rather than sinking into feathery banks of fluffy snowbanks astronauts had to deal instead with a film of electrostatic-charged, clinging and microscopic glassy razor blades. It smelled like gun powder and got into everything, and seemed impossible to clean.

The dark dust of the Moon's immediate surface threatened hatch seals, it scared and tore into spacesuits and, following EVA close-outs became lodged in every conceivable place on an astronaut's body, including up their noses, in their lungs and also lingering in their softest places.

Clearly, "dust mitigation," by then long acknowledged as a real mission and health hazard, came forward as a priority science goal when before new lunar surface expeditions could be carried out. It is accepted as a similar threat to manned travel to Mars, and to the asteroids.

All models of what has become known as a "dynamic" rather than "static" lunar surface include production and trapping of volatile compounds once thought essentially non-existent on the Moon. The speed of this production, it's true dynamics, badly need to be studied before we can return to the Moon with impunity.

Every time an unmanned spacecraft (or a manned lunar module) has landed or taken off from the Moon it's certain some of the dust propelled away by exhaust reaches escape velocity. A larger part of this spiny cloud is put into orbit or on a ballistic path carrying these particles all over the lunar surface. LADEE is designed to establish some natural baseline for this dust before humans start stirring things up. The impact of spacecraft is comparable to the occasional larger natural impact, but hot gas exhaust and its effects is something new.

The delicate bright dust lanes of the Reiner Gamma "swirl albedo" phenomena, stretching at least 550 km southwest from the dormant volcanic Marius domes to the western frontier of Oceanus Procellarum. Seen here in an LROC WAC mosaic from 2010 under early morning shadows. Detailed laser altimetry confirms little to no topographic component, though it does closely correlate with a well-mapped anomalous crustal magnetic field that must be older than exposure to the Sun and space weathering would allow the surface here to remain so bright. Migration of dust, alternately charged and discharged, dislodged by micro-bombardment is alternately attracted and repelled, here, by the local magnetic field lines, keeping the new dust constantly renewed and gathered no more than a meter or so deep [NASA/GSFC/Arizona State University].

Whether or not this was really a guesstimate or hard science, by the time Congress seriously committed to return to the Moon to stay investigators had acknowledged that a kind of primal state existed there that was worth scientific study for its own sake, before human engaged in any "extended activity." And herein is the compelling interest for funding the LADEE mission. It's one way of discovering the state of the lunar exosphere, its dynamics in and out of Earth's extended magnetic field, under a traveling solar incidence, and through a good sampling of lunar days and nights before things inevitably get busy.

The hyperfast laser-based communications and modular spacecraft design for LADEE will be much talked about in reports about this mission, over the next few days and months. That's "all good," as they say, but it might be worth it to also remember the mission's origins going back before Surveyor or Apollo and also offer at least some thanks to the crew of Columbia. We owe the recent renewed short burst in lunar exploration and our added knowledge of the Moon directly to the loss of that spacecraft and crew.

Another lunar mission (and one of only two American missions to the Moon between 1972 and 2009) was also justified as a test platform for new technologies. Now "lost and gone forever," Clementine (1994) spent a year in lunar orbit operated by both NASA and the U.S. Department of Defense. Here Clementine's star-tracking camera finally definitively photographed the "horizon glow" caught previously in the lunar night from the surface by Surveyor 7 and described by Apollo astronauts in lunar orbit twenty years before. This is the phenomena, believed to be back-lit lunar dust, that LADEE is designed to directly sample [NASA/DOD].

And whenever humans eventually return to the Moon for their inevitable extended stay, they will owe much of their preparation to that spacecraft and crew.

Friday, September 6, 2013

Thursday, September 5, 2013

Granular debris flows along the interior wall of Clerke crater, marking a stark contrast in surface reflectance. The crater floor is upper left of this approximately 2 km-wide field of view from LROC Narrow Angle Camera (NAC) observation M183332397R, LRO orbit 12116, February 8, 2012, incidence angle 43.96° full resolution 1.32 meters per pixel from 132.84 km over 20.63°N, 29.76°E [NASA/GSFC/Arizona State University].

Sarah Braden
LROC News System

The interior wall of the Clerke crater has many distinct flows of granular material which narrow as they reach towards the floor of the crater. The source material originates from the crater rim. The debris appear higher in reflectance compared to the rest of the crater wall, likely due to differences in maturity and perhaps grain size of the material.

The debris flows may be younger than the crater floor and walls if the flow was instigated by seismic shaking or a nearby impact crater. The flow may contain more boulders, which may cause the higher reflectance.

Clerke under a high Sun, a low illumination angle of incidence (25°), resulting in an image emphasizing surface reflectance over topographic variation. From an LROC Wide Angle Camera (WAC) monochrome (566 nm) mosaic of two sequential orbital observations captured September 11, 2011; average resolution 60 meters per pixel from 41 km [NASA/GSFC/Arizona State University].

Agnes Mary Clerke was key in increasing public interest in astronomy and astrophysics. She wrote the book A Popular History of Astronomy During the Nineteenth Century (published in 1885), which was written for the non-astronomer. This publication brought her recognition from the astronomy community. Later she wrote Problems in Astrophysics which described her ideas on the direction for future research involving the Sun, stars, and nebulae. Ms. Clerke possessed a great ability to synthesize research results, look at the "big picture" of science, and communicate those ideas to the public as well as scientists. She was elected an honorary member of the Royal Astronomical Society, and an award given (at the time) to only three other women: Caroline Herschel, Mary Somerville, and Margaret Lindsay Huggins.

Alternately, Clerke under a low Sun, and thus a high illumination angle of incidence, resulted in this view of the crater and vicinity in an image greatly emphasizing topographic variation over surface reflectance. LROC GLD100 meter per pixel mosaic, an LROC WAC context showing the proximity of Clerke to the Apollo 17 landing site (red circle) in the Taurus Littrow valley [NASA/GSFC/Arizona State University].

Explore the rest of Clerke crater and the surrounding area in the full NAC, HERE.

Amazing ejecta patterns from small, young craters are always something to look at on the lunar surface. Today's Featured Image displays compositional diversity in fresh ejecta. The broad, low-reflectance streaks of material are likely excavated pyroclastic materials. This approximately 250 m diameter crater is located at 2.162°N, 349.401°E, west of the crater Sommering P.

This low-reflectance material is part of a larger area called a Dark Mantle Deposit (DMD). Dark mantle deposits have lower reflectance compared to surrounding mare basalt areas and are also spectrally distinct from mare basalt. In this case, the dark mantle deposit was likely covered by a thin layer of crater ejecta.

The small crater's location marked with a white circle in an LROC Wide Angle Camera (WAC) context image of a field of view 80 km across [NASA/GSFC/Arizona State University].

The opening image has a low incidence angle of 10° which means the Sun is high in the sky (near local noon). High-sun images are good for revealing differences in the reflectance properties of the surface. Low-sun (large incidence angle) images are better at emphasizing morphology due to topographic shading and shadowing. Incidence angle is the angle between the vector of sunlight and the vector normal to the surface. The WAC context image above has a large incidence angle (taken in early morning) which makes visible the topographic high where the crater was formed. This topographic high is a remnant of highland terrain (kipuka) surrounded by younger mare basalt deposits (smooth, flat areas). There are many other craters on the topographic high that excavate low-reflectance material, which suggests that the whole area is different from the surrounding mare basalt deposits. The high-sun WAC mosaic (below) of the same area shows the locations where the dark mantle deposit is visible. You can learn more about dark mantle deposits here!

LROC WAC monochrome (643 nm) high sun, high reflectance view of the same area as seen in the WAC mosaic immediately above, resolution roughly 100 meters per pixel. Note darker material around the area of the topographic high place [NASA/GSFC/Arizona State University].

Explore the full NAC image HERE to see the other craters excavating low-reflectance material.